A resistive random access memory (hereinafter, referred to as a ReRAM) using for a memory element a variable resistive layer capable of retaining a plurality of resistance states is known. In the related art there has been proposed a ReRAM having a three-dimensional structure in which a plurality of nR-1Tr type strings are disposed above a substrate and in the plurality of nR-1Tr type strings, a plurality of word lines is disposed in a height direction through variable resistive layers on side surfaces of bit lines disposed perpendicular to the substrate and including selection transistors at end portions thereof close to the substrate.
Since a current flows in the ReRAM during a set operation and a reset operation, the word lines and the bit lines are required to have low resistance. In the ReRAM having a three-dimensional structure, there is a case in which the bit lines disposed perpendicular to the substrate are made of polysilicon. In this case, the resistance of polysilicon often has been made low by activation annealing.
On the other hand, there is a case in which an oxygen profile (or an oxygen-deficiency profile) of the variable resistive layers are controlled for the stabilization of the operation of the ReRAM. However, when the activation annealing processing for polysilicon forming the bit lines is performed, the oxygen profile may collapse, it may be difficult to perform accurate control, and the operation of the ReRAM may become unstable.